init: Make WaitToBeReaped() wait less long

Reduce the time spent in WaitToBeReaped() by waiting for SIGCHLD instead
of waiting for 50 ms.

Bug: 308687042
Change-Id: I5e259fdd22dec68e45d27205def2fc6463c06ca3
Signed-off-by: Bart Van Assche <bvanassche@google.com>
diff --git a/init/sigchld_handler.h b/init/sigchld_handler.h
index fac1020..e07a7d6 100644
--- a/init/sigchld_handler.h
+++ b/init/sigchld_handler.h
@@ -25,7 +25,8 @@
 
 void ReapAnyOutstandingChildren();
 
-void WaitToBeReaped(const std::vector<pid_t>& pids, std::chrono::milliseconds timeout);
+void WaitToBeReaped(int sigchld_fd, const std::vector<pid_t>& pids,
+                    std::chrono::milliseconds timeout);
 
 }  // namespace init
 }  // namespace android